Process for depositing a metallic coating on various metal articles or objects



W. HMNES, 03E TOWNSHIIP Oi? SANDVTICH EMT, QNTARIQ, CANADA, m FRANK L. SURENSEN, 0 DETROIT, MICHIGAN, AS$IGN ORS, BY DIRECT AND MESN'E AlSSIG-NMEWS, T0 THE METAL PROTECTION LABQRATOEY, 0E DETLRGIT, MICE- rears, A CGRPORATION Q38 MIGHIGAN..

( IPIROCIESE! DWOSITING A METALLTG COATING 0N VARIOUS METAL ARTTGLZEEZ @EJEGTS.

No Drawing.

To all w hom it may concern:

Be it known that we, FREDERICK W. HAINES, a citizen of the United States, residing in the township of Sandwich East, Province of Ontario, Dominion of Canada, and FRANK. L. SonENsnN, a citizen of the United States, and a resident of Detroit, in the county of Wayne and State of Michigan, have invented a new and useful Process for Depositing a Metallic Coating on 'Various Metal Articles or Objects, of which the following is a full, clear, and exact description.

This invention relates to the coating of metal articles or objects with metal and is applicable to the deposition of thin films of numerous metals upon numerous other metallic bodies, as is frequently desirable for decorative purposes and for the prevention of oxidation, corrosion or rusting.

The objects of our invention are :-The provision of a new and improved process for the deposition, on'metallic articles or objects, of a thin film of various metals, which film cannot be peeled or stripped therefrom; which will provide a protective coating on the said metal articles or objects whereby they will be protected against the action of moisture or other rusting influences; and which film can be deposited in a very short time and with the maximum of certainty and the minimum of expense. Other objects of our invention concern the provision of new and useful compositions of matter or working solutions for use in the formation of such coatings, while further objects and advantages of our invention will become apparent as this description proceeds.

The essence ofour invention consists in the deposition of the metal in question, from a solution of the same, upon a second metal, "by the substitution of a third metal in the solution, and an important feature of our invention is the method employed for restraining and regulating the depositing action so that the film may be closely adherent, fine grained, dense and impervious.

It has long been known that certain metals when immersed in solutions of the salts of other metals will replace those other metals herent so as to Specification of Letters Eatent. Patented NQUWU 22, ll2lln Application filed September 28, 1918. Serial no; 258,123.

in the solution with a reduction of the latter to the metallic state. This tendency for one metal to replace another in solution of its salts depends upon the electrolytic condition of those metals with respect to each other, usually expressed as electrolytic'potential or electrolytic solution pressure. lln the following table based upon recent authorities,

the more common metals are arranged in the order of their electrolytic potential, beginnmg w1th the most positive:

Magnesium, Lead, Alummum, Tin, lgdanganese, jlqlopipeltv inc y rogen Cadmium, #Arsenic, Iron Bismuth, Cobalt, *Antimony. Nickel,

Order uncertain.

In general a metal will replace, from asolution of its salts, any other metal of lower electrolyticpotential, unless the 'diflerence between the potentials is small. The replacement is also infiuenced by the relative concentrations of the difi'erentmetallic ions in the solution. Little or no commercial value has hitherto attended this knowledge, since the metallic deposits so obtained have always been soft, pervious, spongy, friable and imperfectly adherent, "thus possessing neither decorative nor protective qualities.

It has also been known that when certain pairs of metals are immersed into a solution of the salt of some. metal which is more negative than one at least of the firstmetals, the metal in. solution is ordinarily deposited upon both metal bodies; we have discovered that by the employment of proper methods this deposition can be limited to the surface of the more-negative metal and can be rendered so hard,- tough, impervious and adpossess-both decorative and protective qualities of a high order.

In order to accomplish this result we emj ploy a solution containing a very low concentration of the metal or metals to be des ightly soluble compound of the metal to be deposited, the saturation of the solution 5 bem maintained by the presence in the soli form ofian excess of this compound in contact with the liquid. We also ordinarily employ in the solution a quantity of some acid which shall energize the same but without. materially increasing the solubility of the essential compound or independentl attacking the anode metal to any appreciable extent. 1

As a concrete example, suppose it be desired to deposit metallic tin upon the surface of an iron article, we have found the 'follow-.

ing to be a good bath Tin phos hate, Sn,(PO,), 2 ozs. Zinc oxi ,ZnO 2 ozs. 2o Orthohosphoric acid, (H PO,,

y 85%? 1 fluid oz.

Water (to make) 1 gal.

This bath is preferabl used at or near 26 the boiling point and t e iron article is merely immersed therein in contact, either direct or indirect, with the replacing metal ordinarily metallic zinc. The purpose 0 the zinc oxid is to act as a restramer b regulating the acidity of the solution. t is equally possible to add the zinc salt in the form of'zinc phosphate'with a corresponding reduction in the hosphorie acid added. -The tin salt disso ves very sparingly and at the same rate as used. The main advantage of the heating is to keep the contents of the bath thoroughly stirred by the ebullition and convection currents although it also has other advantages.

Deposition'upon the iron will begin immediately and will afford a beautiful, frosted, solid, adherent coating of metallic tin, extremely resistant to atmospheric or salt conditions. While the coating may be sufficiently thick for some pur oses at the end of a few minutes, such as ve minutes, we prefer for most purposes to allow the action to go on for from ten minutes to an hour or more. The size of the article also has some effect, massive articles generally taking a rather longer time than smaller ones; however our invention is independent of the length of time employed since a usable coating will be roduced very promptly while an increase in the thickness thereof will proceed for a considerable time.

Othercompounds' than those of zinc can belused in the solution provided they be compounds of metals which the anode substance Will not reduce to the metallic form. For example,magnesium oxid or aluminum hydroxid can be em loyed with equal facility although we pre er the zinc.

In case we desire to deposit a coatin of .a lead upon a ferrous metal article we ave successfully employed the following for mula:

The ferrous metal article is immersed in the solution (preferably heated to or near the boiling point) in contact, either direct or indirect, with a more positlve metal such as a piece of metallic zinc. The deposit in this case is of darker color. than the tin but is equally firm, adherent, and fine grained.

In case we desire to deposita coating of nickel upon a ferrous metal article we have successfully employed the following solution:

Nickel phosphate Zinc oxid 2 ozs. ()rtho-phosphoric acid 1 oz.

Water (to make) 1 gaL The iron article is immersed in the solution 1 in contact with apiece of zinc as before. 9,0

Furthermore by our invention we are able: to effect deposition upon metals other than"? iron. Thus we are able to deposit upon one coating an additional layer; or la crs of other metals provided that the same e more 95 negative than the anode substance. For example, after having subjected the ferrous metal article, in contact with zinc, to the action of the lead-containing solution above described, the same can be subjected to the action of. atin-contai'ning solution, and a very perfect coating of tin deposited thereon, with corresponding increase in decorative and protecting effect; or after having subjected the ferrous metal article, in contact with zinc, to the action of anyof the solutions above named, the same may be subjected to the action of a solution containing one of several other metals, such as antimony, whereupon an additional coating of that other metal will be secured.

In fact we are able by our invention to deposit simultaneously upon the iron article a plurality of different metals. For example in order to coat iron with lead and; tin 115 simultaneously we have employed with satisfactory results the following solution:

2 ozs.

Tin phosphate 1 oz. Lead oxid 1 oz. Phosphoric acid 1 oz. Water (to make) 1 gal.

The iron article is immersed in the solution (preferably heated) in contact with a piece of zinc as before.

The resulting coating possesses a thickness and i mpermeability'apparently superior to any coating obtainable with either metal alone. In this solution the lead oxid appears to have the same action as the zinc oxid of previous formulae 1 til) so far as regulating the action is concerned; but with this difl'erence that owing to its more negative character it is reduced tp the metallic form.

As another examplefof the deposition of a compound coating we find it possible and frequently desirable toj deposit a c'oating of antimony in conjunction with the other metals heretofore mentioned. For the deposition of a' combined fcoatingof tin and antimony the most successful bath we have yet-discovered is the following:

Tin phosphate (01' hydroxid),

Sn (l?(),) 2 ozs. Zinc chlorid, ZnCl 2 ozs. Boric acid, H BO -i 2 ozs. 'Antimony oxid, Sb O -40'grains.

Water (to make) 1 gal.

zinc can be employed for example, aluminum, which we have used with considerable success for some purposes or magnesium, which is still more positive. The solution tendenc can, if desired, be accelerated, restraine or otherwise modified, by the application of electric potential externally derived.

It will be understood that we do not limit ourselves to the metals mentioned, since other metals in the replacement series can be employed "within the scope of our-invention, either singly, simultaneously, or successively. We do not restrict ourselves to the use of only the particular salts herein suggested or enumerated. And we do not restrict ourselves to the use of the particular restrainers herein set forth, or even to any restrainer. whatever; since in instances where restrainers are desirable it is possible to employ other than zinc compounds.

aving thus described our invention, what we claim is v I 1. The process of coating metal articles by replacement in a solution of the desired coatin -metal, which contains the step of restraining the deposition by placing in the 7 solution an oxid, which in this process is not reduced to its metallic form. r

2. The process of protecting corrodible metal articles which consists in depositing thereon simultaneously a plurality of more negative metals lat a temperature less than the melting point of any of said metals.

3. The process; of coating a metal with a second metal which consists inimmersing the first metal, contact with a third metal more positive electrically than either of the first metals, in jalsaturated solution of some compound of the second metal which is only I slightly soluble;- and meanwhile maintainin 1n contact with sa1d solut1on an excess 0 such slightly sdluble compound a. The process of protecting co'rrodible metal articles which consists in depositing thereon aplurality of la ers of metals eachmore negative than the est.

5. The process of treating ferrous metal articles which consists in immersing the same, in contact with zinc, in a weak solution. of an oxygen compound of one or more metals lying between iron and hydrogen in -the electrolytic potential series, together with a small amount of the oxid of-some metal lying upon" the opposite side of hydrogen in said ser ts:

6. The process of treating ferrous metal articles which consists in immersing the same, in contactjwith zinc, in a weak solution of an oxygen compound of one or more metals lyin between iron and hydrogen in the ,electro yti'c potential series, together with a small amount of oxid of antimony.

v 7. The rocess'of surface treating ferrous metal articles which consists in immersing the same, in contact with zinc, in a solution containing the phosphate of one or more the electrolytic potential series togetherwith a small amount of an oxid of some metal lying upon the opposite side of hydrogen in said series.

' metals lying between iron. and hydrogen in 8. The rocessof surface treating'ferrous metal articles which consists in immersing the same, in contact with zinc, in 'a solution containing thephosphate of one or more metals lying between iron and hydrogen in the electrol ticfpotential series, together with a small amount of antimony trioxid.

.9. The process" of treating ferrous metal with a coatingconsisting of or containing antimony, or a metal adjacent thereto in the electrolytic potential series.

In testimony whereof, we hereunto alfix our signatures. i

FREDERICK w. names. rnann L. sonnnsnn.

articles which consists in covering the same 

